1. Field of the Invention
The present invention relates generally a knock sensor for an internal combustion engine (hereinafter also referred to simply as the engine knock sensor) which incorporates therein a piezoelectric element and is adapted to be fixedly secured on a mounting seat formed in the internal combustion engine for the purpose of detecting vibration of the engine transmitted by way of the mounting seat. More particularly, the present invention is concerned with an engine knock sensor which includes an annular sensor main body and an external connecting portion provided on an outer peripheral surface of the sensor main body and which is designed to be fixedly secured on the mounting seat of the internal combustion engine by means of a clamping member which extends through the sensor main body. Further, the present invention is concerned with a mounting structure for mounting the engine knock sensor.
2. Description of Related Art
At first, description will be directed to the function or operation of the engine knock sensor. Vibration generated by the internal combustion engine is transmitted to the knock sensor mounted on the engine. The vibration of the engine as transmitted to the knock sensor is amplified by means of a weight incorporated in the knock sensor to be subsequently transmitted to a piezoelectric element also incorporated in the knock sensor. In this manner, force of the magnitude which is in proportion to the vibratory acceleration generated by the internal combustion engine is applied to the piezoelectric element, as a result of which a voltage proportional to the distortion of the piezoelectric element makes appearance between electrodes of the piezoelectric element. The voltage generated in this way is taken out by way of an external connecting portion (i.e., portion for allowing the piezoelectric output voltage to be connected to an external unit or equipment) which is provided on an outer peripheral surface of the sensor main body.
In general, the engine knock sensor of the type mentioned above is fixedly secured on a mounting seat formed in the internal combustion engine by means of a clamping member such as a bolt or the like which extends through the main body of the knock sensor. For more particulars, reference may have to be made to, for example, Japanese Patent Application Laid-Open Publication No. 267746/2002 (JP-A-H10-267746), page 3, FIG. 4.
The mounting of the knock sensor of the structure described above is carried out by using the clamping member such as a bolt, screw or the like as mentioned above. Accordingly, even when the orientation of the knock sensor has been set in a predetermined direction before mounting or securing fixedly the knock sensor by means of the clamping member, there may arise such a situation that the knock sensor undergoes rotation or angular displacement upon clamping of the clamping member under the action of clamping torque, which will undesirably result in that a connector, lead wires or the like which serves as the external connecting portion of the knock sensor is positionally deviated from the prescribed position or orientation. In this conjunction, it is further noted that the magnitude of rotation or angular displacement (i.e., the positional deviation) of the knock sensor will vary or change in dependence on the machined or finished state of the mounting seat formed on the engine and/or deposition of oil or lubricant on the mounting seat as well as dispersion of the machining precision of a contact surface of the knock sensor. Such being the circumstances, mounting of the knock sensor on the internal combustion engine has heretofore encountered difficulties or problems that selection of the mounting position of the knock sensor and determination of the layout of a harness extending from the knock sensor are difficult in designing.
Further, for the reasons described above, the work for mounting the knock sensor requires both hands for the mounting operation or manipulation in order to mount the knock sensor with proper or correct orientation in a predetermined direction. Alternatively, a specific tool or tools dedicated for the knock sensor mounting work are required. At any rate, the work efficiency in mounting properly the knock sensor on the internal combustion engine remains to be satisfied, and there thus exists a demand for improvement.